1. Field of the Invention
The present invention relates to a probe unit for testing the electric characteristics of a device under test, i.e., plate-like test substance, such as a semiconductor wafer having the shape of a flat plate, and an inspection head employing the probe unit.
2. Description of the Prior Art
Generally, an inspection i.e., head called a probe card or a probe board is used for the performance test of an integrated circuit. Many conventional inspection heads, i.e., testing heads, are formed merely arranging a plurality of probes in a radial arrangement on a disk-shaped support base. Therefore, the conventional inspection heads are able to inspect only some chips formed on a semiconductor wafer simultaneously and take much time for inspecting one semiconductor wafer on which many integrated circuit chips are formed.
An inspection head disclosed in Japanese Patent Application Public Disclosure No. 7-201935 intended to solve the foregoing problems is provided with a plurality of probe units each provided with a plurality of probes arranged on the lower edge of a support member having the shape of a flat plate extending horizontally. In this prior art inspection head, however, electrical interference occurs between the adjacent probes, particularly, between signal probes and power probes because the probes are arranged in a single layer on the lower edge of the support member. Such electrical interference introduces great noise which exerts a harmful influence on inspection into signals on signal lines, particularly into signals on the signal probes.